This invention relates to the field of wireless integrated circuits.
The demand for low-cost, reliable wireless communications continues to increase at a rapid rate, as do the demands on the technologies enabling such communications. Chip designers work on many fronts to find ways to make the circuitry found inside devices such as cellular phones smaller, cheaper, easier to fabricate, less power-hungry, and more reliable.
One major component in a cellular phone is a radio frequency (RF) transceiver. U.S. Pat. No. 6,049,702 shows a block diagram of the RF/analog and analog/digital (A/D) interface circuitry of a basic transceiver, which can be combined with other components (not shown) to form a complete transceiver. The transmitter portion of the transceiver includes digital-to-analog converters (DACs), low-pass filters for filtering the outputs of DACs, respectively, and a modulator that performs a frequency conversion on signals received at its inputs and which is driven by a phase-locked loop (PLL) circuit that includes a reference voltage-controlled-oscillator (VCO) and a resonator (tank circuit). The modulator's output is fed to a power amplifier, and the amplified output is fed to one side of a transmit/receive (T/R) switch, filtered with a bandpass filter, and connected to an antenna.
The receiver portion is connected to the other side of T/R switch. Incoming signals are received by the antenna and filtered by the bandpass filter before being fed to a low-noise amplifier (LNA)/demodulator circuit. The output of the circuit's LNA is passed through a bandpass filter before being fed to a demodulator which performs a frequency conversion on the signal received by antenna. The demodulator is driven by a PLL circuit which includes a reference VCO and a tank circuit. The demodulator output drives an intermediate-frequency automatic gain control (IF AGC) stage, with a bandpass filter interposed between the stage's IF amplifier and its AGC circuitry. The AGC output is fed to an IF demodulator which is driven by a PLL circuit that includes a reference VCO and a tank circuit. The IF demodulator's two outputs are passed through respective low-pass filters before being fed to respective analog-to-digital converters (ADCs).
Current RF transceivers are implemented using a variety of device technologies For example, DACs, ADCs, and all other digital baseband transceiver circuitry are typically CMOS circuits. The modulator, LNA/demodulator, IF/AGC stage, and IF demodulator generally use bipolar junction transistors (BJTs). The power amplifier can be fabricated on a gallium arsenide (GaAs) substrate, particularly for a high-power application such as a cellular phone Bandpass, lowpass filters, as well as tank circuits, and antenna are generally built with discrete components. T/R switch is also typically made from discrete components, or are made from costly, complex PIN diode circuits if integrated.
Because a variety of technologies must be combined, current transceivers typically requires multiple integrated circuits (IC). For example, a CDMA or WCDMA RF front end typically consists of two ICs. There is a receive IC and a transmit IC, which need to be on separate pieces of silicon to isolate the low power received signal (around 10 mW) from the high power send signal (around 300 mW). With a processor IC to control the RF front-end, the electronic of an RF system requires three chips: a processor IC, a receive IC, and a transmit IC. These ICs add cost and can result in an assembly is typically larger than is desired, particularly when the limited space and weight requirements imposed on designers of battery-powered handheld devices must be met.